Air conditioning systems for motor vehicles are known which contain refrigerant fluids which generally are halogen compounds such as FREON, which is known in the industry as R-12. These compounds, when released into the Earth's atmosphere, are believed to be carried to the stratosphere, where they cause catalytic decomposition of the ozone, and hence cause environmental harm by increasing the amount of ultraviolet radiation reaching Earth's surface. For this reason, R-12 has been banned, as well as some other halogen-based refrigerants.
Prior art air conditioning systems for motor vehicles are generally of an open drive type. Motive power for the compressor is supplied by a shaft passing through the pressure boundary which contains the refrigerant. The shaft seals are subject to leaks which release the refrigerant to the atmosphere, and the shaft seals additionally introduce power losses due to friction.
These prior art systems are generally operated at variable speeds which depend on the speed of the engine of the motor vehicle. The need for the air conditioning system to provide sufficient cooling regardless of the speed at which it is driven necessitates design considerations which cause considerable power losses.
Prior art systems require an electromechanical device to alternatively connect the shaft of the compressor to a pulley driven by the motor of the vehicle and to disconnect the shaft of the compressor from the pulley. This electromechanical device is usually a solenoid which engages a clutch which connects the belt drive to the compressor. The solenoid draws significant electrical current whenever the air conditioner is in use, and thus introduces additional power losses.
These prior art systems also cause power loss even when the air conditioner is not in use because of the belt drive to the compressor.
Prior art systems also place a variable load on the engine of the vehicle. As the air conditioner cycles on and off, the load it places on the engine varies. This introduces a safety hazard, because the cycling occurs unexpectedly, and if the vehicle is in close proximity to other vehicles, the operator of the vehicle must respond quickly to changes in power demand of the air conditioner.
One prior attempt to provide a vehicular air conditioning system eliminates the open drive and the shaft seal of the systems discussed above. This system uses a DC motor located inside the pressure envelope. The DC motor is powered by the car's DC electrical system. Such an approach has the disadvantage that the brushes of the DC motor are subject to wear, require maintenance, and hence cause further releases of refrigerant to the atmosphere.
Additional background information is available from the art of window air conditioners for buildings. These have AC electrical motors inside a pressure envelope, and do not require a shaft seal. Power for the electrical motor is obtained from the wiring system of the building in which the air conditioner is mounted. This power is introduced into the pressure envelope by conduction paths which penetrate the pressure envelope, and are insulated from it. The unit is totally sealed from the atmosphere by brazed seals, so that loss of the refrigerant does not occur.
Information regarding the properties of some presently available refrigerants is presented in the following publications by DuPont Chemicals Inc., the teachings of which are incorporated herein by reference thereto.
Safety of SUVA* Refrigerants (AS-1) PA1 DuPont SUVA* HP Refrigerants (P-HP)